U.S. patent application number 12/002636 was filed with the patent office on 2008-08-14 for method of mobile radio positioning aided by single fan self-surveying laser transmitter.
This patent application is currently assigned to TRIMBLE NAVIGATION LTD. Invention is credited to Mark E. Nichols.
Application Number | 20080192242 12/002636 |
Document ID | / |
Family ID | 39685530 |
Filed Date | 2008-08-14 |
United States Patent
Application |
20080192242 |
Kind Code |
A1 |
Nichols; Mark E. |
August 14, 2008 |
Method of mobile radio positioning aided by single fan
self-surveying laser transmitter
Abstract
A method of mobile radio positioning aided by a single fan
self-surveying laser transmitter (SF_SS_LT), wherein a rover
comprises a mobile radio positioning system (Mobile_RADPS)
integrated with a mobile laser detector; and wherein THE SF_SS_LT
comprises a single fan laser transmitter and a positioning system
integrated with the single fan laser transmitter. The method
comprises: (A) performing self-surveying of the (SF_SS_LT); (B)
generating a single fan laser beam by using the single fan laser
transmitter; (C) detecting the single fan beam by using the mobile
laser detector; and (D) timing the fan laser beam strike at the
rover's location and using the timing of the fan laser beam strike
at the rover's location to improve an accuracy in determination of
position coordinates of the rover.
Inventors: |
Nichols; Mark E.;
(Christchurch, NZ) |
Correspondence
Address: |
Law Offices of Boris G. Tankhilevich
Suite A, 536 North Civic Drive
Walnut Creek
CA
94597
US
|
Assignee: |
TRIMBLE NAVIGATION LTD
|
Family ID: |
39685530 |
Appl. No.: |
12/002636 |
Filed: |
December 17, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11010224 |
Dec 11, 2004 |
7310137 |
|
|
12002636 |
|
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Current U.S.
Class: |
356/139.01 ;
342/357.27; 342/357.41; 342/357.47 |
Current CPC
Class: |
G01S 19/10 20130101;
G01S 19/44 20130101; G01S 19/04 20130101 |
Class at
Publication: |
356/139.01 |
International
Class: |
G01B 11/24 20060101
G01B011/24 |
Claims
1. A method of mobile radio positioning aided by a single fan
self-surveying laser transmitter (SF_SS_LT), wherein a rover
comprises a mobile radio positioning system (Mobile_RADPS)
integrated with a mobile laser detector; and wherein said SF_SS_LT
comprises a single fan laser transmitter and a positioning system
integrated with said single fan laser transmitter; wherein said
positioning system is configured to obtain the coordinate
measurements of said single fan laser transmitter; said method
comprising: (A) performing self-surveying of said (SF_SS_LT); (B)
generating a single fan laser beam by using said single fan laser
transmitter; (C) detecting said single fan beam by using said
mobile laser detector; and (D) timing said fan laser beam strike at
said rover's location and using said timing of said fan laser beam
strike at said rover's location to improve an accuracy in
determination of position coordinates of said rover.
2. The method of claim 1, wherein said step (A) further comprises:
(A1) providing a stationary radio positioning system (RADPS)
receiver integrated with said single fan laser transmitter, said
stationary RADPS receiver having a stationary radio antenna;
wherein the distance between a phase center of said stationary
radio antenna and said single fan laser transmitter is known and
fixed; (A2) providing a wireless communication device configured to
receive a set of differential corrections data; and (A3) obtaining
precise coordinate measurements of said single laser transmitter by
using said stationary radio positioning system (RADPS) receiver
configured to utilize said set of differential corrections
data.
3. The method of claim 1, wherein said step (B) further comprises:
(B1) mechanically rotating said fan laser transmitter head about
its vertical axis at a substantially constant angular rate.
4. The method of claim 3, wherein said step (B1) further comprises:
(B1, 1) controlling said substantially constant angular rate of
said rotation of said fan laser transmitter head about its vertical
axis by using a phase oscillator.
5. The method of claim 3, wherein said step (B1) further comprises:
(B1, 2) enhancing said substantially constant angular rate of said
rotation of said fan laser transmitter head about its vertical axis
by giving said laser transmitter head a substantially sufficient
mass.
6. The method of claim 1, wherein said step (B) further comprises:
(B2) optically rotating said fan laser transmitter about its
vertical axis at said substantially constant angular rate.
7. The method of claim 1, wherein said step (B) further comprises:
(B3) generating an electronic timing pulse every time a known
position of said laser beam passes a single reference mark in said
laser transmitter; (B4) generating a plurality of time tags by
time-tagging each said electronic timing pulse by using said
SF_SS_LT; (B5) generating a low-passed filtered estimate of an
angular rate of said laser beam by using said plurality of time
tags; wherein each said time tag is indicative of a time instant
when said reference mark is crossed by one said electronic timing
pulse; and (B6) transmitting said low-passed filtered estimate of
angular rate of said laser beam and transmitting said plurality of
time tags to said rover via said wireless communication link.
8. The method of claim 1, wherein said step (B) further comprises:
(B7) generating a main electronic timing pulse every time a known
position of said laser beam passes a main reference mark; (B8)
generating an additional electronic timing pulse every time a known
position of said laser beam passes an additional reference mark;
(B9) generating a plurality of main time tags by time-tagging each
said main electronic timing pulse by using said SF_SS_LT; (B10)
generating a plurality of additional time tags by time-tagging each
said additional electronic timing pulse by using said SF_SS_LT;
(B11) generating a first low-passed filtered estimate of an angular
rate of said laser beam by using said plurality of main time tags;
wherein each said main time tag is indicative of a time instant
when said main reference mark is crossed by one said main
electronic timing pulse; (B12) generating a second low-passed
filtered estimate of an angular rate of said laser beam by using
said plurality of additional time tags; wherein each said
additional time tag is indicative of a time instant when said
additional reference mark is crossed by one said additional
electronic timing pulse; (B13) averaging said first low-passed
filtered estimate of said angular rate of said laser beam and said
second low-passed filtered estimate of said angular rate of said
laser beam; and (B14) transmitting said averaged low-passed
filtered estimate of angular rate of said laser beam; transmitting
said plurality of main time tags, and transmitting said plurality
of additional time tags to said rover via said wireless
communication link.
9. The method of claim 1, wherein said step (C) further comprises:
(C1) detecting at least one light pulse generated by said laser
transmitter by using said mobile laser detector; wherein each said
light pulse corresponds to one said single sloping fan laser beam
strike at said rover's location; and (C2) receiving said low-passed
filtered estimate of angular rate of said laser beam and receiving
said plurality of time tags.
10. The method of claim 1, wherein said step (C) further comprises:
(C3) detecting at least one light pulse generated by said laser
transmitter by using said mobile laser detector; wherein each said
light pulse corresponds to one said single sloping fan laser beam
strike at said rover's location; and (C4) receiving said averaged
low-passed filtered estimate of angular rate of said laser beam,
receiving said plurality of main time tags, and receiving said
plurality of additional time tags.
11. The method of claim 1, wherein said step (D) further comprises:
(D1) measuring the time difference between the time instance when
said light pulse corresponding to said single sloping fan laser
beam strike at said rover's location is received and the latest
main reference crossing time corresponding to the time instance
when said known position of said laser beam passes said main
reference mark at the location of said laser transmitter; and (D2)
calculating a height of said rover with improved accuracy based on
position coordinates of said rover and based on said time
difference measured at said step (D1), wherein said position
coordinates of said rover are interpolated position coordinates
interpolated between position coordinates taken at GPS time Epoch
immediately preceding said laser strike and position coordinates
taken at GPS time Epoch immediately after said laser strike.
12. The method of claim 11, wherein said step of (D2) further
comprises: (D2, 1) providing a differential mobile radio
positioning system (Mobile_RADPS); (D2, 2) receiving a second
plurality of external radio signals broadcasted by at least one
radio source selected from the group consisting of: {GPS; GLONASS;
combined GPS/GLONASS; GALILEO; Global Navigational Satellite System
(GNSS); and a pseudolite transmitter} by using said differential
mobile radio positioning system (Mobile_RADPS); and (D2, 3)
receiving a second set of differential corrections data broadcasted
by at least one source selected from the group consisting of: {a
Base Station, an RTK Base Station; a Virtual Base Station (VBS);
and a pseudolite transmitter} by using said differential mobile
radio positioning system (Mobile_RADPS); wherein said differential
mobile radio positioning system (Mobile_RADPS) is configured to
utilize said second plurality of external radio signals and said
second set of differential corrections data to obtain position
coordinates of said rover.
13. The method of claim 11 further comprising: (D3) optimizing said
improved height calculation of said rover.
14. The method of claim 13, wherein said step (D3) further
comprises: (D3, 1) calculating a set of sensitivity parameters
selected from the group consisting of: {a partial derivative of
said rover's height with respect to a laser beam rotation
frequency; a partial derivative of said rover's height with respect
to a horizontal distance from said rover to said laser transmitter;
a partial derivative of said rover's height with respect to a time
difference between said actual laser strike time and said expected
laser strike time; and a partial derivative of said rover's height
with respect to a vertical angle}.
15. The method of claim 13, wherein said step (D3) further
comprises: (D3, 2) calculating said variable laser beam rotation
frequency by using said plurality of time tags corresponding to
time-tagging of said laser beam to each said additional reference
mark at said laser transmitter location.
16. The method of claim 11 further comprising: (D4) calibrating
said improved height calculation of said rover for planar errors
affecting the planarity of said single fan beam.
17. The method of claim 1, wherein said rover comprises an
implement, wherein said implement is selected from the group
consisting of: {a blade or a bucket on an earthmoving machine; an
agricultural implement; and a device connected to a machine,
wherein the device's location is being controlled}; said method
further comprising: (E) determining position coordinates of said
implement with improved accuracy.
18. The method of claim 17, wherein said step (E) further
comprises: (E1) sending to said SF_SS_LT position coordinates of
said implement.
19. The method of claim 1, wherein said SF_SS_LT further comprises
a display unit; said method further comprising: (F) displaying
position coordinates of said implement.
20. The method of claim 1 further comprising: (G) controlling the
movement of said implement.
Description
[0001] This is a continuation-in-part of the U.S. patent
application Ser. No. 11/010,224, entitled "A SELF SURVEYING LASER
TRANSMITTER", and filed on Dec. 11, 2004.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention.
[0003] The current invention relates to position tracking and
machine control systems, and, more specifically, to a combination
of single fan laser systems and global navigation satellite systems
configured to include self surveying capabilities in addition to
having tracking and machine control capabilities.
[0004] 2. Discussion of the Prior Art.
[0005] The parent patent application discloses a self-surveying
laser transmitter comprising a laser transmitter configured to
generate at least one rotating laser beam and a radio positioning
system integrated with the laser transmitter. The radio positioning
system was configured to obtain the precise coordinate measurements
of the laser transmitter by utilizing the differential corrections
transmitted from the Base Station by using the wireless
communication link.
SUMMARY OF THE INVENTION
[0006] The present invention discloses a method of mobile radio
positioning aided by a single fan self-surveying laser transmitter
(SF_SS_LT), wherein a rover comprises a mobile radio positioning
system (Mobile_RADPS) integrated with a mobile laser detector; and
wherein the SF_SS_LT comprises a single fan laser transmitter and a
positioning system integrated with the single fan laser
transmitter.
[0007] In one embodiment, the method of mobile radio positioning of
the present invention comprises: (A) performing self-surveying of a
single fan self-surveying laser transmitter (SF_SS_LT); (B)
generating a single fan laser beam by using the single fan laser
transmitter; (C) detecting the single fan beam by using the mobile
laser detector; and (D) timing the fan laser beam strike at the
rover's location and using the timing of the fan laser beam strike
at the rover's location to improve an accuracy in determination of
position coordinates of the rover.
[0008] In one embodiment of the present invention, the step (A)
further comprises: (A1) providing a stationary radio positioning
system (RADPS) receiver integrated with the single fan laser
transmitter, wherein the stationary RADPS receiver includes a
stationary radio antenna; wherein the distance between a phase
center of the stationary radio antenna and the single fan laser
transmitter is known and fixed; (A2) providing a wireless
communication device configured to receive a set of differential
corrections data; and (A3) obtaining precise coordinate
measurements of the single laser transmitter by using the
stationary radio positioning system (RADPS) receiver configured to
utilize the set of differential corrections data.
[0009] In one embodiment, wherein the SF_SS_LT further comprises a
display unit, the method of mobile radio positioning of the present
invention comprises: displaying the position coordinates of the
implement; and controlling the movement of the implement.
BRIEF DESCRIPTION OF DRAWINGS
[0010] The aforementioned advantages of the present invention as
well as additional advantages thereof will be more clearly
understood hereinafter as a result of a detailed description of a
preferred embodiment of the invention when taken in conjunction
with the following drawings.
[0011] FIG. 1 depicts the single fan self-surveying laser
transmitter (SF_SS_LT).
[0012] FIG. 2 illustrates the single fan self-surveying laser
transmitter (SF_SS_LT) and at least one mobile unit including a
laser detector and a mobile radio positioning system (RADPS)
receiver.
[0013] FIG. 3 is a timing diagram that illustrates how a low-passed
filtered estimate of the single fan laser transmitter rotation rate
is first generated by using the time series of zero crossings.
[0014] FIG. 4 illustrates the geometry of the laser beam and
observed height difference.
DETAILED DESCRIPTION OF THE PREFERRED AND ALTERNATIVE
EMBODIMENTS.
[0015] Reference will now be made in detail to the preferred
embodiments of the invention, examples of which are illustrated in
the accompanying drawings. While the invention will be described in
conjunction with the preferred embodiments, it will be understood
that they are not intended to limit the invention to these
embodiments. On the contrary, the invention is intended to cover
alternatives, modifications and equivalents that may be included
within the spirit and scope of the invention as defined by the
appended claims. Furthermore, in the following detailed description
of the present invention, numerous specific details are set forth
in order to provide a thorough understanding of the present
invention. However, it will be obvious to one of ordinary skill in
the art that the present invention may be practiced without these
specific details. In other instances, well known methods,
procedures, components, and circuits have not been described in
detail as not to unnecessarily obscure aspects of the present
invention.
[0016] In one embodiment of the present invention, FIG. 1 depicts
the single fan self-surveying laser transmitter (SF_SS_LT) 10
comprising: a single fan laser transmitter 12 configured to
generate a single laser beam 14, a stationary radio positioning
system (RADPS) receiver 16 integrated with the laser transmitter
12, and a wireless communication device 18. In this embodiment, the
radio positioning system (RADPS) 16 is configured to obtain the
coordinate measurements of the single fan laser transmitter 12.
[0017] The stationary radio positioning system (RADPS) receiver 16
integrated with the single fan laser transmitter 12 provides a
number of benefits to a potential user comparatively with a system
that mechanically combines a laser system and a RADPS receiver
system. Indeed, the stationary radio positioning system (RADPS)
receiver 16 integrated with the single fan laser transmitter 12 has
the reduced cost as opposed to the cost of the combined laser and
RADPS system because the integrated system requires only one set of
packaging, can utilize a shared computer memory and can use a
common power supply. In the integrated system the laser beam and
the electrical phase center of the RADPS stationary antenna are
separated by a known and fixed distance (not shown), wherein in the
mechanically combined system the distance between the laser beam
and the electrical phase center of the RADPS stationary antenna is
prone to errors because this distance is introduced by an operator
of the integrated system.
[0018] In one embodiment of the present invention, a 3-D laser
station generates at least one rotating fan-shaped laser beam 14.
The 3D Laser Station that generates at least one rotating
fan-shaped laser beam is disclosed in U.S. Pat. Nos. 6,870,608 and
6,643,004. Both U.S. Pat. Nos. 6,870,608 and 6,643,004 are
incorporated herein in their entirety.
[0019] Referring still to FIG. 1, the stationary radio positioning
system (RADPS) receiver 16 can be selected from the group
consisting of: {a GPS receiver; a GLONASS receiver; a combined
GPS/GLONASS receiver; a GALILEO receiver; a Global Navigational
Satellite System (GNSS) receiver; and a pseudolite receiver}.
[0020] The Global Positioning System (GPS) is a system of satellite
signal transmitters that transmits information from which an
observer's present location and/or the time of observation can be
determined. Another satellite-based navigation system is called the
Global Orbiting Navigational System (GLONASS), which can operate as
an alternative or supplemental system. ON more satellite-based
navigation system is a GALILEO system.
[0021] Reference to a Satellite Positioning System or RADPS herein
refers to a Global Positioning System, to a Global Orbiting
Navigation System, to GALILEO System, and to any other compatible
Global Navigational Satellite System (GNSS) satellite-based system
that provides information by which an observer's position and the
time of observation can be determined, all of which meet the
requirements of the present invention, and to a ground based radio
positioning system such as a system comprising of one or more
pseudolite transmitters.
[0022] After the RADPS receiver determines the coordinates of the
i-th RADPS satellite by demodulating the transmitted ephemeris
parameters, the RADPS receiver can obtain the solution of the set
of the simultaneous equations for its unknown coordinates (x0, y0,
z0) and for unknown time bias error (cb). The RADPS receiver can
also determine velocity of a moving platform.
[0023] A pseudolite comprises a ground based radio positioning
system working in any radio frequency including but not limited to
the GPS frequencies and the ISM (industrial scientific medical)
unlicensed operation band, including 900 MHZ, 2.4 GHz, or 5.8 GHz
bands ISM bands, or in a radio location band such as the (9.5-10)
GHz band. Pseudolites can be used for enhancing the GPS by
providing increased accuracy, integrity, and availability.
[0024] The complete description of the pseudolite transmitters in
GPS band can be found in "Global Positioning System: Theory and
Applications"; Volume II, edited by Bradford W. Parkinson and James
J. Spilker Jr., and published in Volume 164 in "PROGRESS IN
ASTRONAUTICS AND AERONAUTICS", by American Institute of Aeronautics
and Astronautics, Inc., in 1966.
[0025] In ISM band, including 900 MHZ, 2.4 GHz, or 5.8 GHz bands,
the user can own both ends of the ISM communication system. The ISM
technologies are manufactured by Trimble Navigation Limited,
Sunnyvale, Calif. Metricom, Los Gatos, Calif. and by Utilicom,
Santa Barbara, Calif.
[0026] Pseudolites as radio positioning systems can be configured
to operate in ISM band.
[0027] The following discussion is focused on a GPS receiver,
though the same approach can be used for a GLONASS receiver, for a
GPS/GLONASS combined receiver, GALILEO receiver, or any other RADPS
receiver.
[0028] In one embodiment, the RADPS receiver 16 (of FIG. 1) can
comprise a differential GPS receiver. In differential position
determination, many of the errors in the RADPS signals that
compromise the accuracy of absolute position determination are
similar in magnitude for stations that are physically close. The
effect of these errors on the accuracy of differential position
determination is therefore substantially reduced by a process of
partial error cancellation. Thus, the differential positioning
method is far more accurate than the absolute positioning method,
provided that the distances between these stations are
substantially less than the distances from these stations to the
satellites, which is the usual case. Differential positioning can
be used to provide location coordinates and distances that are
accurate to within a few centimeters in absolute terms. The
differential GPS receiver can include: (a) a real time code
differential GPS; (b) a post processing differential GPS; (c) a
real-time kinematic (RTK) differential GPS that includes a code and
carrier RTK differential GPS receiver.
[0029] The differential GPS receiver can obtain the differential
corrections from different sources.
[0030] Referring still to FIG. 1, in one embodiment of the present
invention, the differential GPS receiver 16 can obtain the
differential corrections from a Base Station 28.
[0031] The fixed Base Station (BS) placed at a known location
determines the range and range rate measurement errors in each
received GPS signal and communicates these measurement errors as
corrections to be applied by local users. The Base Station (BS) has
its own imprecise clock with the clock bias CB.sub.BASE. As a
result, the local users are able to obtain more accurate navigation
results relative to the Base Station location and the Base Station
clock. With proper equipment, a relative accuracy of 5 meters
should be possible at distances of a few hundred kilometers from
the Base Station.
[0032] Referring still to FIG. 1, in another embodiment of the
present invention, the differential GPS receiver 16 can be
implemented by using a TRIMBLE Ag GPS -132 receiver that obtains
the differential corrections from the U.S. Coast Guard service free
in 300 kHz band broadcast by using the wireless communication
device 18 and the wireless communication link 30. In this
embodiment, the self-surveying laser transmitter 12 integrated with
the differential GPS receiver 16 should be placed within (2-300)
miles from the U.S. Coast Guard Base Station. The accuracy of this
differential GPS method is about 50 cm.
[0033] Referring still to FIG. 1, in one embodiment of the present
invention, the differential corrections can be obtained from the
Wide Area Augmentation System (WAAS) by using the wireless
communication device 18 and the wireless communication link 30. The
WAAS system includes a network of Base Stations that uses
satellites (initially geostationary satellites-GEOs) to broadcast
GPS integrity and correction data to GPS users. The WAAS provides a
ranging signal that augments the GPS that is the WAAS ranging
signal is designed to minimize the standard GPS receiver hardware
modifications. The WAAS ranging signal utilizes the GPS frequency
and GPS-type of modulation, including only a Coarse/Acquisition
(C/A) PRN code. In addition, the code phase timing is synchronized
to GPS time to provide a ranging capability. To obtain the position
solution, the WAAS satellite can be used as any other GPS satellite
in satellite selection algorithm. The WAAS provides the
differential corrections free of charge to a WAAS compatible user.
The accuracy of this method is better than 1 meter.
[0034] Referring still to FIG. 1, in one embodiment of the present
invention, the real time kinematic (RTK) differential GPS receiver
16 can be used to obtain the position locations with less than 2 cm
accuracy. The RTK differential GPS receiver receives the
differential corrections from the Base Station 28 placed in a known
location within (10-50) km by using the wireless communication
device 18 and the wireless communication link 30. For a high
accuracy measurement, the number of whole cycle carrier phase
shifts between a particular GPS satellite and the RTK GPS receiver
is resolved because at the receiver every cycle will appear the
same. Thus, the RTK GPS receiver solves in real time an "integer
ambiguity" problem that is the problem of determining the number of
whole cycles of the carrier satellite signal between the GPS
satellite being observed and the RTK GPS receiver. Indeed, the
error in one carrier cycle L1 (or L2) can change the measurement
result by 19(or 24) centimeters, which is an unacceptable error for
the centimeter level accuracy measurements.
[0035] Referring still to FIG. 1, in one embodiment of the present
invention, the differential corrections can be obtained by the
RADPS receiver 16 from the Virtual Base Station (VBS) 28 by using
the wireless communication device 18 and the wireless communication
link 30.
[0036] Indeed, the Virtual Base Station (VBS) is configured to
deliver a network-created correction data to a multiplicity of
rovers via a concatenated communications link consisting of a
single cellular connection, and a radio transmission or
broadcasting system. The location of the radio transmitting system
can be co-located with a GPS Base Station designated as the
position of the local Virtual Reference Station. This GPS Base
Station determines its position using GPS, and transmits its
location to the VRS Base Station via a cellular link between the
local GPS Base Station and the VRS Base Station. It enables the VRS
Base Station to generate differential corrections as if such
differential corrections were actually being generated at the real
GPS Base Station location. These corrections can be delivered to
the self-surveying laser transmitter 12 by using a wireless
communication link 30 and wireless communication device 18.
[0037] An article "Long-Range RTK Positioning Using Virtual
Reference Stations," by Ulrich Vollath, Alois Deking, Herbert
Landau, and Christian Pagels, describing VRS in more details, is
incorporated herein as a reference in its entirety, and can be
accessed at the following URL:
http://trl.trimble.com/dscgi/ds.py/Get/File-93152/KIS2001-Paper-LongRange-
.pdf.
[0038] Referring still to FIG. 1, in one embodiment of the present
invention, the wireless communication link 30 can be implemented by
using a variety of different embodiments.
[0039] In general, the wireless communication link 30 (of FIG. 1)
can be implemented by using a radio wave frequency band, an
infrared frequency band, or a microwave frequency band. In one
embodiment, the wireless communication link can include the ISM
band, including 900 MHZ, 2.4 GHz, or 5.8 GHz bands, wherein the
user can own both ends of the ISM communication system.
[0040] In one embodiment of the present invention, the wireless
communication link 30 (of FIG. 1) can be implemented by using the
Trimble SiteNet.RTM. 900 private radio network. The Trimble
SiteNet.RTM. 900 private radio network is a rugged, multi-network,
900 MHz radio modem designed specifically for the construction and
mining industries. It is used to establish robust, wireless data
broadcast networks for real-time, high-precision GPS applications.
This versatile Trimble radio operates in the frequency range of
902-928 MHz, broadcasting, repeating, and receiving real-time data
used by Trimble GPS receivers. Under optimal conditions, the
SiteNet 900 radio broadcasts data up to 10 km (6.2 miles)
line-of-sight and coverage can be enhanced by using a network of
multi-repeaters. Using the SiteNet 900 radio as a repeater, enables
one to provide coverage in previously inaccessible or obstructed
locations. The SiteNet 900 radio is so versatile, that one can
easily change its operating mode to suit any network configuration.
This reduces costs and maximizes uptime. Additionally, SiteNet 900
is license free in the U.S.A. and Canada, which makes it extremely
portable. One can move it from project to project without licensing
hassles and restrictions. The SiteNet 900 radio is designed to
operate reliably in demanding RF environments where many other
products and technologies cannot. Optimized for GPS with increased
sensitivity and jamming immunity, the SiteNet 900 radio also has
error correction, and a high-speed data rate, ensuring maximum
performance. The SiteNet 900 radio is especially suited for use
with Trimble's SiteVision.RTM. GPS grade control system, and is
ideal for all GPS machine control applications where reliability is
important. The machine-rugged unit has been designed and built
especially for harsh construction and mining environments. Fully
sealed against dust, rain, splash, and spray, the SiteNet 900 radio
remains reliable in all weather. The radio's ruggedness and
reliability minimizes downtime, lowering ownership costs. Trimble's
SiteNet 900 radio can be used with any Trimble GPS receiver,
including: MS750, MS850, MS860, and 5700 receivers.
[0041] In one embodiment of the present invention, the wireless
communication link 30 (of FIG. 1) can be implemented by using a 1.8
GHz band that supports the personal communications services (PCS).
The PCS uses the international standard DCS-1800. Yet, in one more
embodiment, the wireless communication link can include a real time
circuit switched wireless communication link. For instance, the
wireless communication link employing a real time circuit switched
wireless communication link can include the Iridium satellite
system produced by Motorola, Schaumburg, Ill.
[0042] In one additional embodiment, the wireless communication
link can be implemented by using a system of Low Earth Orbiting
Satellites (LEOS), a system of Medium Earth Orbiting Satellites
(MEOS), or a system of Geostationary Earth Orbiting Satellites
(GEOS) which can be used to store and to forward digital packet
data. For instance, the LEOS systems in (20-30) GHz range are
manufactured by Cellular Communications located in Redmond, Wash.,
and the LEOS systems in (1.6-2.5) GHz range are produced by
Loral/Qualcomm located in San Diego, Calif.
[0043] The wireless communication link can include a cellular
telephone communication means, a paging signal receiving means,
wireless messaging services, wireless application services, a
wireless WAN/LAN station, or an Earth-satellite-Earth communication
module that uses at least one satellite to relay a radio wave
signal. The wireless communication link can also include the
cellular telephone communication means that can include an Advanced
Mobile Phone System (AMPS) with a modem. The modem can comprise a
DSP (digital signal processor) modem in 800 MHz range, or a
cellular digital packet data (CDPD) modem in 800 MHz range. The
cellular digital communication means includes a means of modulation
of digital data over a radio link using a time division multiple
access (TDMA) system employing format IS-54, a code division
multiple access (CDMA) system employing format IS-95, or a
frequency division multiple access (FDMA). The TDMA system used in
Europe is called groupe special mobile (GSM) in French.
[0044] For the purposes of the present invention, a cellular
telephone communication means can be used to get a wireless access
to the Internet in order, for example, to broadcast the real time
coordinates of the self-surveying laser transmitter position on a
special web-site.
[0045] Referring still to FIG. 1, the wireless communication device
18 can be implemented by using any of devices that can be
configured to provide: {a cellular link; a radio link; a private
radio band link; a SiteNet 900 private radio network link; a link
to the wireless Internet; and a satellite wireless communication
link}. A person skillful in the art can easily identify all these
devices. Please, see the discussion above.
[0046] In one embodiment of the present invention, the wireless
communication device 18 is configured to respond to specific
requests from a mobile equipment (not shown) transmitted over the
wireless communication link 30.
[0047] Referring still to FIG. 1, in one embodiment of the present
invention, the laser transmitter 12 comprises a fan laser
transmitter configured to generate a single fan laser beam 14 that
rotates continuously about a vertical axis at a uniform rate above
a known stationary point in the plot of land.
[0048] Referring still to FIG. 1, in one embodiment, the apparatus
of the present invention 10 further comprises a distance measuring
device 32 integrated with the single fan laser transmitter 12 and
integrated with the RADPS receiver 16. In this embodiment, the
distance measuring device 32 is configured to measure the distance
between the phase center of the stationary radio antenna (not
shown) and a known point or reference plane 36 over which the
single fan self-surveying laser transmitter (SF_SS_LT) is
positioned in order to determine the position coordinates of the
single laser transmitter in relation to the known point or
reference plane.
[0049] The GlobalSpec Inc., located at 350 Jordan Rd, Troy, N.Y.,
12180, manufactures a wide range of Electronic Distance Measurement
(EDM) tools that can be used to implement the distance measurement
device 32. More specifically, a special laser "gun" beam can be
used to measure very precisely the time it takes for a laser beam
to make the round-trip from the "gun" to the reflectors, and back.
Using this time, the known speed that the laser travels (the speed
of light), and correcting for air temperature and pressure, the
distance can be determined to a precision of 1 part per million
(i.e. 1 mm over a distance of 1 km).
[0050] Referring still to FIG. 1, in one embodiment, the apparatus
of the present invention 10 further comprises a tilt angle
measurement device 34 integrated with the single laser transmitter
12 and integrated with the RADPS receiver 16. In this embodiment,
the tilt measurement device 34 is configured to perform tilt
coordinates measurements of the phase center of the stationary
radio antenna (not shown) in relation to the known reference
surface over which the single fan self-surveying laser transmitter
(SF_SS_LT) is positioned in order to determine the position
coordinates of the single laser transmitter 12 in relation to the
known reference surface 38.
[0051] In one embodiment, the tilt angle measurement device 34
further comprises an electronic tilt measurement device. The
Precision Navigation, Inc., (PNI) based in Mountain View, Calif.
manufactures TCM2 Electronic Compass Sensor Module. TCM2 is a
high-performance, low-power electronic compass sensor that offers
compass heading, pitch and roll through an electronic interface to
host system. This high end system provides a robust heading
reference system that can be easily integrated with a GPS
navigational system. The Precision Navigation, Inc., (PNI) also
manufactures a low end, low cost Vector-VR Head Positioning Sensor
that provides a 3 DOF attitude sensor whose combination of
tilt-performance, low-power, and low-cost makes it ideally suited
for tilt-measurement applications.
[0052] In one embodiment of the present invention, FIG. 2
illustrates the single fan self-surveying laser transmitter
(SF_SS_LT) 71, a first wireless communication link 62, a stationary
wireless communication device 64 configured to receive a set of
differential corrections data by using the first wireless
communication link 62, at least one mobile unit 76 including a
laser detector 80 and a mobile radio positioning system (RADPS)
receiver 82, and at least one second wireless communication link
74.
[0053] At least one second wireless communication link 74 is used
to substantially continuously transmit to at least one mobile unit
76 the precise coordinate measurements of the single fan laser
transmitter 66 and the set of differential corrections obtained by
the stationary RADPS receiver 68. At least one mobile RADPS
receiver 82 utilizes the differential corrections to obtain the
precise coordinate measurements of the mobile unit 76 via the
second wireless communication link 74.
[0054] The mobile RADPS receiver 82 is selected from the group
consisting of: {a GPS receiver; a GLONASS receiver; a combined
GPS/GLONASS receiver; a GALILEO receiver; a Global Navigational
Satellite System (GNSS) receiver; and a pseudolite receiver}.
[0055] In one embodiment, the stationary RADPS 68 and the mobile
RADPS 82 are selected to include the same satellite receiver
configured to receive the same satellite signals.
EXAMPLE I
[0056] Both the mobile RADPS receiver 82 and the stationary RADPS
receiver 68 are selected to include a GPS receiver configured to
receive the satellite signals from the GPS satellite-vehicles SV1
52, SV2 54, SV 56, and SV 58.
[0057] The second wireless communication link 74 can be implemented
by using a the same vehicles as the first wireless link 62, for
instance, a cellular link; a radio link; a private radio band link;
a SiteNet 900 private radio network link; a link to the wireless
Internet; and a satellite wireless communication link.
EXAMPLE II
[0058] The first wireless communication link 62 is implemented by
using a cellular phone link to connect to Virtual Base Station,
whereas the second wireless communication link is implemented by
using a SiteNet 900 private radio network link.
[0059] Referring still to FIG. 2, the single fan laser transmitter
66 generates a single fan-beam 72. In one embodiment of the present
invention, the beam is rotated about a vertical axis at a very
constant angular rate 4 rad/s. The frequency of rotation is given
by f (Hz), while the period of rotation is T seconds. The following
relationship exists between the angular parameters:
.omega. = 2 .pi. T = 2 .pi. .times. f [ rad / s ] ( 1 )
##EQU00001##
The laser transmitter 66 head (not shown) is rotated within good
bearings and is driven by a motor which is phase oscillator locked.
Furthermore, the laser transmitter head is given sufficient mass to
enhance the constant rotation rate of the fan-beam. The present
rotation rate is 40 to 50 Hz.
[0060] An electronic timing pulse is generated every time the
center of the laser beam 72 passes a zero direction mark (not
shown) in the laser transmitter 66. The timing pulse is accurately
(typically to within 40 nanoseconds) time tagged within the
position coordinates of the transmitter 66 (determined by the
Stationary _RADPS 68) and is denoted
[0061] The rotating rate of the laser is typically 50-60 Hz. A
low-passed filtered estimate of the spin rate can be readily
generated from the zero-direction crossing times. This information
is then transmitted to the rover unit 76 using the wireless device
64 via the second wireless data link 74 that is preferably also
used for the RADPS differential angular rate data.
[0062] It will be shown later that variations in the spin rate of
the laser directly impact on the accuracy of height estimates of
the rover 76. Apart from careful manufacture of the rotating laser
head, it is possible to comprise additional timing marks at say
every .pi./4 radians of rotation where RADPS time stamps are made.
Differences between the observed and expected time-tags at the
.pi./4; .pi./2; 3.pi./4 reference points provide a laser correction
mechanism for users of the laser signals.
[0063] The zero direction crossing times are sent to the rover 76
via the second wireless communication link 74. If necessary,
additional rotation rate variation parameters can also be
comprised.
[0064] In one embodiment of the present invention, the rover unit
76 is mounted on a mast (not shown) for machine control
applications or on a portable pole (not shown) for hand-held
construction setup etc, or on the cab of a machine. The rover 76
includes an integrated laser detector 80 and Mobile_RADPS receiver
82 that tracks radio (or satellite signals). The laser detector 80
is capable of detecting the light pulse generated by the single fan
laser transmitter 66. The leading and/or trailing edge of the pulse
are time-stamped using the Mobile_RADPS receiver 82 to accuracy
better than 100, typically about 40 nanoseconds.
[0065] In one embodiment of the present invention, as was disclosed
above, the Mobile_RADPS receiver 82 comprises a differential
Mobile_RADPS receiver that receives differential corrections from
any other source of the differential correction stream.
[0066] In one embodiment of the present invention, the differential
Mobile_RADPS receiver is capable of computing its location relative
to the laser transmitter 66 to within a few centimeters using
real-time kinematic (RTK) techniques. However, the precision of the
height component of the rover is appreciably worse with RADPS
techniques compared with the laser positioning.
[0067] In one embodiment of the present invention, the height of
the rover (not shown) is determined at the rover's location by
using the laser detector 80 according to the following
procedure.
[0068] At the first step, as shown in FIG. 3 in timing diagram 170,
a low-passed filtered estimate of the laser transmitter 66 rotation
rate is first generated using the time series of zero crossings:
[0069] T (1) 172; T (2) 176; T (3) 180; T (4) 184; T (5) 188; T (n)
The timing diagram 170 also illustrates the timings of laser
strikes t.sub.strike (1) 174, t.sub.strike (2) 176, t.sub.strike
(3) 182, and t.sub.strike (4) 186 at the laser detector's location.
Let f.sub.filt be the low-passed filtered rotation frequency, and
T.sub.filt, be the corresponding period of rotation.
[0070] At the next step, the laser detector 80 is configured to
measure the time difference between the received laser pulse
(strike) and the last zero crossing time:
t.sub.diff(i)=t.sub.strike(i)-.tau.(i); (2)
where: [0071] t.sub.diff(i) is the difference between the laser
strike time at epoch i and the corresponding zero crossing time;
[0072] (i) is the time of the zero crossing for epoch i; [0073]
t.sub.strike(i) is the time of the laser strike at epoch i.
[0074] In practice, laser strikes may be received prior to knowing
the last zero crossing time. This delay is due mainly to the time
taken to time-stamp the zero crossing times and broadcast and
receives them. Eq. (2) can be modified according to:
t.sub.diff(i)=t.sub.strike(i)-[.tau.(i-m)+T.sub.filt.times.m];
(3)
where: [0075] (i-m) is the zero cross time m-rotations ago, [0076]
T.sub.filt is the low-passed filtered rotation period (in seconds),
[0077] m are an integer number of rotations.
[0078] At the next step, the Mobile_RADPS receiver 82 determines
the horizontal and vertical rover's location relative to the laser
transmitter 66 to within a few centimeters. The azimuth of the
rover unit is then derived from:
.alpha. = tan - 1 ( E T - E R N T - N R ) . ( 4 ) ##EQU00002##
[0079] In an actual system, one would allow an orientation of the
laser transmitter to be arbitrary and the reference orientation can
be determined from the measured laser azimuth angle and the GPS
vector from the stationary to the mobile RADPS.
[0080] However, at the following step, assuming the laser
transmitter 66 is aligned to true north, and that the laser
transmitter 66 and rover 76 are at the same height, then the laser
strike time will be given by:
t.sub..alpha.(i)=.pi.(i)+.alpha.(i).times..omega.; (5)
where: [0081] t.sub..alpha.(i) is the expected laser strike time
for the rover at azimuth, and at the same height as the
transmitter; .alpha. (i) is the azimuth of the rover relative to
the transmitter at epoch i; w is the angular rate of rotation of
the transmitter head, as defined in Eq. (1).
[0082] At the next step, one assumes that, in general, the rover 76
will lie above or below the height of the laser transmitter 66. If
this is the case, the actual laser strike time will differ from
that obtained in Eq. (5). It is this time difference, t.sub.obs,
which enables one to precisely compute the height of the rover 76,
where:
t.sub.obs(i)=t.sub.strike(i)-t.sub..alpha.(i). (6)
[0083] FIG. 4 is a diagram 200 that illustrates the geometry of the
laser beam and observed the height difference 204. More
specifically, the diagram 200 illustrates the view looking back
towards the laser transmitter 66 (of FIG. 2) from outside the rover
76 (of FIG. 2). The fan beam 72 is inclined at an angle, .theta.
radians, 202, as shown. Let point F 206, be the intersection of the
fan-beam 208, a horizontal plane at the height of the transmitter
210, and the vertical plane containing the laser detector (D) 214.
Point G 212, is vertically beneath D 214 and in the same plane as F
206. The observed time difference t.sub.obs, described in Eq. (6)
can be converted to an equivalent angle subtended at the laser
transmitter via:
.phi.(i)=.omega..times.t.sub.obs(i). (7)
[0084] The position coordinates of the rover are interpolated
position coordinates interpolated between position coordinates
taken at GPS time Epoch immediately preceding the laser strike and
position coordinates taken at GPS time Epoch immediately after the
laser strike.
[0085] The described above height determination process is affected
by a number of parameters. It is useful to analyze the impact of
the uncertainty in each parameter on the height difference. With
this knowledge, it is possible to optimize the system design.
[0086] In one embodiment of the present invention, the position
coordinates of the implement can be determined with improved
accuracy as was disclosed above. Therefore, the movement of the
implement can be controlled, which could be important in certain
applications. The implement is selected from the group consisting
of: {a blade or a bucket on an earthmoving machine; an agricultural
implement; and a device connected to a machine, wherein the
device's location is being controlled}.
[0087] If RADPS device 68 (of FIG. 2) if it is equipped with the
display device (not shown), the movement of the mobile unit 76 and
the movement of the implement (not shown) can be displayed on the
display device.
[0088] The foregoing description of specific embodiments of the
present invention has been presented for purposes of illustration
and description. They are not intended to be exhaustive or to limit
the invention to the precise forms disclosed, and obviously many
modifications and variations are possible in light of the above
teaching. The embodiments were chosen and described in order to
best explain the principles of the invention and its practical
application, to thereby enable others skilled in the art to best
utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated. It
is intended that the scope of the invention be defined by the
claims appended hereto and their equivalents.
* * * * *
References